A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section induces air from the surrounding environment into the engine and accelerates a fraction of the air toward the compressor section. The remaining fraction of air is accelerated into and through a bypass plenum, and out the exhaust section. The compressor section, which may include a high pressure compressor and a low pressure compressor, raises the pressure of the air it receives from the fan section to a relatively high level. The compressed air then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel into a plenum. The injected fuel is ignited to produce high-energy compressed air. The air then flows into and through the turbine section causing turbine blades therein to rotate and generate energy. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass plenum.
To increase operational efficiency, one or more bearing assemblies may be included in various sections of the engine. In one example, a bearing assembly is implemented in the high pressure compressor. In such case, the bearing assembly may be mounted through a bore to a high speed rotor and may include a split face inner race, an outer race, and a ball element supported therebetween. The split face inner race includes a forward ring and an aft ring. A cage may be included between the split face inner race and the outer race to maintain circumferential positioning of the bearing balls. In this regard, the cage may have a forward rail and an aft rail between which the bearing balls may be disposed.
Because the rotor, and hence, portions of the bearing assembly, may rotate at high speeds (e.g., greater than 2×106 dN, where d is the bearing bore diameter in millimeters and the N is the speed of the rotor in revolutions per minute), lubricant may be used to reduce friction and to provide cooling to the bearing assembly. The lubricant may be delivered to the bearing assembly via a plurality of axial and radial grooves that make up a lubrication system. Conventionally, a first section of the axial grooves are formed on an inner surface of the forward ring, and a second section of the axial grooves may be formed on an inner surface of the aft ring. The forward and aft rings are held together by a pin to maintain the first and second section of the axial grooves in alignment with each other. The radial grooves communicate with the axial grooves to feed lubricant to the cage rails and the bearings.
Although the aforementioned lubrication system has been adequate for lubricating the high pressure compressor bearing assembly, it may be improved. In particular, use of a pin to maintain the necessary alignment between the forward and aft rings may cause unwanted stress concentration in certain areas of the bearing assembly during high speed applications. Additionally, in high speed applications, the split face inner race may experience a waviness condition, which may not allow substantially even circumferential distribution of the lubricant to the cage rails and bearings. Consequently, premature bearing wear may occur.
Accordingly, it is desirable to have a system that provides substantially even circumferential distribution of lubricant around the split face inner ring during operation. Additionally, it is desirable for the system to be capable of distributing the lubricant to the forward and aft rails of a cage and to the bearings at a desired ratio. Moreover, it is desirable to for the system to be capable of providing lubrication, regardless of how the forward and aft rings are oriented relative to each other. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.